Poorly Soluble, Low Toxicity (PSLT) Polymer Category: A Case Study for An Integrated

Approach to Testing and Assessment (IATA) under the Toxic Substances Control Act (TSCA)

Louis ScaranoSenior Advisor, New Chemicals DivisionOffice of Pollution Prevention & ToxicsU.S. Environmental Protection Agency

Shawn AndersonGlobal Regulatory and Strategy LeaderEngineered Polysaccharides Venture

Health and BiosciencesIFF

Disclaimer: The views expressed in this presentation are those of the presenters. Mention of trade names of commercial products should not be interpreted as an endorsement.

Inhalation Webinar Series

May 26, 2021

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Topics Covered

• TSCA Reform

• High-molecular weight (HMW) Polymers

• Default approaches

• TSCA New Chemical Categories

• TSCA Section 4 (h) – Reduction of Testing on Vertebrates

• Case Study on Biosolubility: α-1,3-glucan

• Updates to the TSCA New Chemical Categories

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TSCA Reform

• On June 22, 2016, the Frank R. Lautenberg Chemical Safety for the 21st Century Act (Lautenberg Chemical Safety Act) was signed into law. The Lautenberg Chemical Safety Act amended the Toxic Substances Control Act (TSCA), the nation’s primary chemicals management law.

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• Prior to June 2016, certain new chemical substances were “dropped” during EPA’s 90-day review period

• After June 2016, EPA applied default approaches to hazard and exposure for these same types of substances that led to unreasonable risks

HMW Polymers

• High-molecular weight (HMW) polymers (i.e., NAMW > 10,000 Daltons) are those substances that meet the E2 criteria and are manufactured or used as particles with sizes in the respirable range (i.e., < 10 µm)

• May cause inhalation hazards, including lung overload via a specific mode of action (i.e., impairment of alveolar-macrophage [AM] mediated clearance), as identified in rat inhalation studies

• Overload is defined in this presentation as when the exposure concentration is sufficiently high or the duration sufficiently long to overwhelm AM-mediated clearance.

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HMW Polymers – Default Approach

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Toxicologicalanalogues

• Benchmark MOE consisted of 10x for intraspecies, 10x for interspecies, and 1x for BMDL or 10x for LOAEC = 100 or 1000

• If the calculated MOE is lower than the benchmark MOE, then EPA interprets this as an unreasonable risk

HMW Polymers – Default Approach

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• For findings of unreasonable risk, EPA is required to take risk management actions (e.g., consent orders with testing requirements, restrictions on manufacturing, processing, use, disposal, etc.) to address unreasonable risks before a company may commence manufacture or processing of the new chemical substance.

• The default approach was applied to a novel α-1,3-glucan, which resulted in risk findings and risk management actions:

HMW Polymers – Default Approach

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• The SNUR requirements were consistent with EPA’s hazard concerns and testing recommendations for the Respirable, Poorly Soluble Particulates Chemical Category

Limited to MMAD, no wt% cutoff

Limited to effects on the lung

Limited to in vivo testing

2002 Respirable, Poorly Soluble Particulates Category

Amended TSCA: Section 4(h)

• However, the amended TSCA states “The Administrator shall reduce and replace,

to the extent practicable, scientifically justified, and consistent with the policies

of this title, the use of vertebrate animals in the testing of chemical substances or

mixtures…” (Section 4(h)(1))

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Celluloseb(1,4) linkage

Starchα(1,4) linkage

Polysaccharides extracted from plants are widely used as industrial ‘bulk’ polymers to provide unique end-

use applications but are limited by processes and raw material source. Nature often produces mixtures.

Xanthan Gum

Alginates Locust Bean Gum

Case Study: α-1,3-glucan

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α-1,3-glucanCH2OH

HOH

O

H

O

H

H

H

O

H

O

CH2OHHO

CH2O

H

H

O

H

H

O

H

SUCROSE

BIOCATALYST

Polysaccharide

Applications

Coatings

Fibers & Fiber Additives

Composites

Packaging

Using enzymatic polymerization to create a variety

of polymer structures with unique product features

and application benefits

Case Study: α-1,3-glucan

O

OH

O OH

OH O

O

OH O

OHOH

N

Glucanα (1,3) linkage

Powderα-1,3-glucan

88% solidsParticle size control:

Unground - 150 micron40 micron17 micron

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Case Study: α-1,3-glucan

0

2

4

6

8

10

12

14

0.1 1 10 100

Vo

lum

e D

ensi

ty (

%)

Particle Diameter (µm)

IFF polymer

Xerox toner (Muhle et al.)

Silica 50 mg/m3 (Lee & Kelly)

Bimodal size distribution characterization for ground α-1,3-glucan

Particle size distribution of ground α-1,3-glucan

Solubility Determination

Multi-faceted Strategic Approach in response to EPA’s Risk Assessment taking into consideration in chemico, in silico and in vitro alternatives to animal studies• Exposure monitoring results for

manufacturing including grinding• Demonstrated no reduction in PSD

upon cross country transport• Re-examined Solubility using SELF

according to Boisa et al• Performed MPPD modeling to

predict deposition, clearance and lung burden over a simulated long term exposure to the IFF polymer

• Explored in vitro alternatives to characterize AOP

Parameter Value

Density 1.5 kg/m3

Circularity 0.875 native, 0.84 ground

Aspect ratio 1.355 native, 1.354 ground

Zeta Potential ~0

Characterization for native and ground α-1,3-glucan

Source: Ladics et al. (2021) CHEMICAL RESEARCH IN TOXICOLOGY,

available at: A Weight-of-the-Evidence Approach for Evaluating in Lieu of Animal Studies, the Potential of a Novel Polysaccharide Polymer to Produce Lung Overload

% Distribution Size (μm)

d10 3.1

d50 9.2

d90 392.8

0.0 <0.2

Case Study: α-1,3-glucan

• In chemico biosolubilitytests were performed in water, Gamble solution, and simulated epithelial lung fluid (SELF) at 37 oC and pH 7.0-7.5 for 10- or 30-days

• α-1,3-glucan was found to be biosoluble in SELF, but not in water or Original Gamble’s solution Source: Ladics et al. (2021) CHEMICAL RESEARCH IN TOXICOLOGY, at p. “G” (Table 5), available at: A Weight-of-the-

Evidence Approach for Evaluating in Lieu of Animal Studies, the Potential of a Novel Polysaccharide Polymer to Produce Lung Overload

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Case Study: α-1,3-glucan

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• A simple exponential decay model was applied to the 10-day test data set to predict solubility in SELF:

• Where P(t) is the amount of some quantity at time t, P0 is the initial amount at time t = 0, λD is the decay rate, and t is time

• The half-life was estimated to be 66 days (time at which 50% of the polymer is dissolved in SELF)

Case Study: α-1,3-glucan

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In silico modeling was performed using the Multiple-Path Particle Dosimetry (MPPD) model to predict deposition, clearance, and lung burden over the course of a simulated long-term exposure to the α-1,3 glucan

MPPD predictions were validated with experimental measurements of lung burden in rats exposed to 9000 Toner (see slide 5)

The empirical clearance model in MPPD was modified to account for the dissolution rate of the α-1,3-glucan using the following:

• Where a, b, c, and d are fitted model coefficients, mA is the lung burden in the alveolar airways, and λD is the dissolution rate for the α-1,3-glucan obtained from the biosolubility experiments

Case Study: α-1,3-glucan

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Human equivalent concentrations (HECs) were calculated for the 9000 Toner exposure concentrations and for the α-1,3-glucan at the same concentration

HECs for the α-1,3-glucan polysaccharide were about 100 times larger than those for the 9000 Toner

Source: Ladics et al. (2021) CHEMICAL RESEARCH IN TOXICOLOGY, at pp. “I” and “J” (Tables 8 and 9), available at:

https://doi.org/10/1021/acs.chemrestox.0c00301 or A Weight-of-the-Evidence Approach for Evaluating in Lieu of Animal Studies, the Potential of a Novel Polysaccharide Polymer to Produce Lung Overload

Case Study: α-1,3-glucan

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EPA concluded:

Case Study: α-1,3-glucan

• Based on these findings, EPA determined that the α-1,3-glucan would not overload the lungs at the predicted worker exposure levels and concluded there was no need to conduct animal studies

• EPA revoked the SNUR restricting the manufacturing and use of the α-1,3-glucan, effective September 24, 2020

Amended TSCA: Section 4(h)

• The IFF contributions laid the groundwork for further refinements to EPA’s evaluations on HMW polymers

• EPA collaborated with external partners, including NGOs and members of industry to further determine the breadth of non-animal test methods that could be used that provide information of equivalent or better scientific quality and relevance in accordance with Section 4(h) of TSCA

• This collaboration led to refinements to the HMW polymer category and inclusion/exclusion criteria, which removed the MW cutoff and included respirability, solubility, reactivity, and biosolubility.

TSCA New Chemicals Program (NCP) Chemical Categories

2021 Draft PSLT Polymer Category

ate or an i ate

espirable P

Pol mer

E clu e

s it ater E tractable

s it apol mer

s it espirable

s it eac e

s it iosoluble eets

40 0(b)

100 m

es

es

es

1 ei ht o par cles ith A 10 m

o o

ee able 1

100 m inAr cial air a linin ui (e , Gambles or E ) 1 m inAr cial l sosomal ui

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E clu e E clu e

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Acknowledgements

EPA• Todd Stedeford• Tala Henry• William Irwin

IFF Case Study• Greg Ladics• Owen Price, ARA• Shantanu Kelkar• Scott Herkimer

Thank you!